Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $229.84   5.724%   $242.996   $243.00   $243.00   $243.00  
  Purchase #2 $205.35   12.615%   $231.2549   $231.25   $231.25   $231.30  
  Purchase #3 $37.63   5.630%   $39.7486   $39.75   $39.75   $39.70  
  Purchase #4 $242.45   5.491%   $255.7629   $255.76   $255.75   $255.80  
  Purchase #5 $88.71   8.454%   $96.2095   $96.21   $96.20   $96.20  
  Purchase #6 $187.95   5.137%   $197.605   $197.61   $197.60   $197.60  
  Purchase #7 $55.49   7.831%   $59.8354   $59.84   $59.85   $59.80  
  7 purchase totals = $1,047.42       $1,123.4123   $1,123.42   $1,123.40   $1,123.40